Improve info.

README.md

@@ -1,3 +1,83 @@
 # BSV - Backup, Synchronization, Versioning
 
-Readme to be done.
+Bsv is a tool to perform backups, file/directory synchronization between devices and light versioning. It's architecture is inspired from git, but focus on backup first, synchronization second and as a byproduct also allow versioning.
+
+Bsv is in a very early stage of development and is not production ready yet.
+
+
+## Development setup
+
+Bsv currently only supports Python >= 3.11. Once you have a compatible Python version, just fetch the code and install bsv in editable mode in a virtual env:
+
+```
+git clone https://git.draklia.net/draklaw/pybsv.git
+cd pybsv
+python -m venv venv
+. venv/bin/activate
+pip install -e .[test]
+```
+
+This will automatically install the dependencies (including `pytest`). Happy hacking !
+
+
+## Roadmap
+
+### v0.0.1 - Simple CAS + insert/remove files manually
+
+Basic features. Naïve CAS implementation that store everything in a single big file with no option for removing objects. Supports a single "local" repository.
+
+- [x] Simple CAS implementation (it's OK if it's naïve).
+- [x] Content-based chunking to store files.
+- [x] `bsv init` command to initialize bsv.
+- [x] `bsv info` print useful information bsv configuration.
+- [ ] `bsv log` show the history of snapshots.
+- [ ] `bsv show <digest>` show the object `digest`.
+- [ ] `bsv ls <bsv-path>` list files in a bsv directory.
+- [ ] `bsv mkdir <bsv-path>` create a directory in bsv directly.
+- [ ] `bsv add [-r] <fs-path> <bsv-path>` copy files from the filesystem to bsv.
+- [ ] `bsv get [-r] <bsv-path> <fs-path>` copy files from bsv to the filesystem.
+- [ ] `bsv rm [-r] <bsv-path>` create a directory in bsv directly.
+
+### v0.0.2 - File map + snapshots
+
+Add support for mapping files from BSV virtual file system to the actual file system. Add snapshot and restore commands.
+
+- [ ] `bsv map` list mappings between bsv paths and filesystem paths.
+- [ ] `bsv map add <bsv-path> <fs-path>` add a mapping.
+- [ ] `bsv map remove <bsv-path> <fs-path>` remove a mapping.
+- [ ] `bsv snapshot` capture a snapshot, i.e. ensure that mapped files in the repositories match what is on the filesystem.
+- [ ] `bsv restore <snapshot> <fs-path>` update files on the filesystem to the version captured by `snapshot`.
+
+### v0.0.3 - Multiple repository
+
+Support multiple repository. Repository can be configured to store only metadata (typically for the local repository) or everything.
+
+- [ ] Support repositories that store only metadata.
+- [ ] `bsv repo [-v]` list all known repositories.
+- [ ] `bsv repo create <name> <destination>` create a new repository.
+- [ ] `bsv repo add [<name>] <destination>` add an already existing repository.
+- [ ] `bsv repo remove <name>|<destination>` remove a repository.
+- [ ] `bsv fetch [<name>]` fetch latest metadata from known repositories.
+- [ ] `bsv sync` similar to `snapshot` + `fetch` + `restore`: Fetch latest changes from the repositories and update the filesystem to match. In case of conflict (file changed both in the repositories and locally), performs a snapshot first to ensure all conflicting versions are backed'up, then use some conflict-resolution strategy and warn the user.
+
+### v0.0.4 - Proper CAS
+
+- [ ] Safe concurrent access (e.g. when several devices use a shared repository).
+- [ ] Support removing objects.
+- [ ] Garbage collection (remove unreferenced objects).
+- [ ] Use garbage collection to keep metadata-only repository clean.
+
+### v0.0.5 - Some extra features
+
+- [ ] `bsv tag <name> [<snapshot>] [-m <message>]` set/update a tag (an alias to a specific snapshot).
+- [ ] Support for symlinks.
+
+### Later
+
+- [ ] `bsv watch` starts a daemon that watch changes in mapped directories and automatically create snapshots.
+- [ ] `bsv http` starts an http server that expose an API + an interface to manipulate BSV. Allow to list files, explore history, download and upload files...
+- [ ] Bsv protocol + client/server
+- [ ] Custom rules for repository to select what must be stored or not.
+    - [ ] Create sensible rules for backup (keep a lot of recent versions, less for older versions).
+- [ ] Add object set support (a kind of object that simply store a collection of objects). Can be used as tag.
+- [ ] Add mail object ?

pyproject.toml

@@ -13,6 +13,7 @@ classifiers = [
 dynamic = ["version"]
 dependencies = [
     "fastcdc",
+    "rich",
     "tomlkit",
 ]
 
@@ -22,9 +23,8 @@ test = [
 ]
 
 [project.urls]
-# TODO
-# "Homepage" = "https://github.com/pypa/sampleproject"
-# "Bug Tracker" = "https://github.com/pypa/sampleproject/issues"
+"Homepage" = "https://git.draklia.net/draklaw/pybsv"
+"Bug Tracker" = "https://git.draklia.net/draklaw/pybsv/issues"
 
 [project.scripts]
 bsv = "bsv.main:main"

src/bsv/cli.py

@@ -0,0 +1,126 @@
+# bsv - Backup, Synchronization, Versioning
+# Copyright (C) 2023  Simon Boyé
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from __future__ import annotations
+
+from typing import Any, Callable, TypeVar
+
+from rich.console import Console
+from rich.text import Text
+
+
+_console: Console | None = None
+def get_console() -> Console:
+    assert _console is not None
+    return _console
+
+_error_console: Console | None = None
+def get_error_console() -> Console:
+    assert _error_console is not None
+    return _error_console
+
+
+def init_consoles(color: str="auto"):
+    global _console
+    global _error_console
+
+    assert _console is None
+    assert _error_console is None
+
+    kwargs: dict[str, Any] = {
+        "tab_size": 4,
+    }
+    match color:
+        case "always":
+            kwargs["force_terminal"] = True
+        case "auto":
+            pass
+        case "never":
+            kwargs["no_color"] = True
+
+    _console = Console(
+        **kwargs,
+    )
+    _error_console = Console(
+        stderr = True,
+        **kwargs,
+    )
+
+
+PromptType = TypeVar("PromptType")
+
+class NoDefaultType:
+    def __repr__(self):
+        return "NoDefault"
+NoDefault = NoDefaultType()
+
+def prompt(
+    prompt: str,
+    factory: Callable[[str], PromptType],
+    *,
+    console: Console | None = None,
+    default: PromptType | NoDefaultType = NoDefault,
+    show_default: bool = True,
+) -> PromptType:
+    if console is None:
+        console = get_console()
+
+    prompt_text = Text(prompt, style="prompt")
+    prompt_text.end = ""
+    if show_default and default is not NoDefault:
+        prompt_text.append(" ")
+        prompt_text.append(f"({default})", style="prompt.default")
+    prompt_text.append(": ")
+
+    while True:
+        try:
+            value = console.input(prompt_text)
+        except KeyboardInterrupt:
+            console.print("")
+            raise
+
+        if not value and not isinstance(default, NoDefaultType):
+            return default
+        try:
+            return factory(value)
+        except ValueError as err:
+            console.print(err)
+
+def prompt_confirmation(prompt: str, *, console: Console | None=None, default: bool=True) -> bool:
+    if console is None:
+        console = get_console()
+
+    prompt_text = Text(prompt, style="prompt")
+    prompt_text.end = ""
+    prompt_text.append(" ")
+    if default:
+        prompt_text.append("(Y/n)", style="prompt.default")
+    else:
+        prompt_text.append("(y/N)", style="prompt.default")
+    prompt_text.append(": ")
+
+    while True:
+        try:
+            value = console.input(prompt_text).strip().lower()
+        except KeyboardInterrupt:
+            console.print("")
+            raise
+
+        if not value and not isinstance(default, NoDefaultType):
+            return default
+        if value not in "yn":
+            console.print("Please answer 'y' or 'n'.")
+        else:
+            return value == "y"

src/bsv/command/info.py

@@ -19,6 +19,7 @@ from argparse import ArgumentParser
 from pathlib import Path
 
 from bsv import __version__
+from bsv.cli import get_console
 from bsv.command import command
 from bsv.repository import Repository
 
@@ -33,27 +34,29 @@ def init_parser(parser: ArgumentParser):
     )
 
 @command(init_parser)
-def info(repository_path: Path | None, verbosity: int=0) -> int:
+def info(config_path: Path, verbosity: int=0) -> int:
     """Print informations about bsv: config file used, known repository, file mapping...
     """
 
-    print(f"bsv v{__version__}")
+    print = get_console().print
 
-    if repository_path is None:
-        print("Repository path not found. Bsv is likely not setup on this device.")
+    print(f"bsv [green]v{__version__}")
+
+    if not config_path.exists():
+        print("bsv configuration not found. Bsv is likely not setup on this device.", style="red")
         return 0
-    else:
-        print(f"Repository path: {repository_path}")
 
-    repo = Repository(repository_path)
+    repo = Repository(config_path)
 
-    print(f"Repository name: {repo.name}")
+    print(f"[blue]Config path: [bold yellow]{repo.config_path}")
+    print(f"[blue]Device name: [bold yellow]{repo.device_name}")
+    print(f"[blue]Local repository: [bold yellow]{repo._local_repository_path}")
 
-    if repo.path_map:
-        print("Path map: (bsv path <-> filesystem path)")
-        for pair in sorted(repo.path_map):
+    print("[blue]Path map:[/blue] (bsv path <-> filesystem path)")
+    if repo.path_map.pairs:
+        for pair in sorted(repo.path_map.pairs):
             print(f"    {pair.bsv} <-> {pair.fs}")
     else:
-        print("Path map is empty.")
+        print("  [bold yellow]No path mapped.")
 
     return 0

src/bsv/command/init.py

@@ -16,35 +16,40 @@
 from __future__ import annotations
 
 from argparse import ArgumentParser
-from os import getlogin
 from pathlib import Path
 import platform
 
 from bsv.command import command
+from bsv.repository import check_config_path, check_device_name, check_local_repository_path, create_repository
+from bsv.util import default_local_repository_path
 
 
 def init_parser(parser: ArgumentParser):
-    parser.add_argument(
-        "--name", "-d",
-        help = "Name of the repository. Default to system hostname.",
-    )
     parser.add_argument(
         "--interactive", "-i",
+        default = False,
         action = "store_true",
         help = "Prompt the user for configuration choices.",
     )
     parser.add_argument(
-        "destination",
+        "--local-repository", "-l",
         type = Path,
+        default = default_local_repository_path(),
         nargs = "?",
+        dest = "local_repository_path",
         help = "Path to a non-existing or empty folder where bsv data will be stored.",
     )
+    parser.add_argument(
+        "--device-name", "-n",
+        default = platform.node(),
+        help = "Name of the device. Default to system hostname.",
+    )
 
 @command(init_parser)
 def init(
-    repository_path: Path | None,
-    destination: Path | None = None,
-    name: str | None = None,
+    config_path: Path,
+    device_name: str,
+    local_repository_path: Path,
     interactive: bool = False,
 ) -> int:
     """Initialize a new bsv repository.
@@ -52,60 +57,62 @@ def init(
     from datetime import datetime as DateTime
     import tomlkit
 
-    if name is None:
-        name = platform.node()
+    from bsv.cli import get_console, get_error_console, prompt, prompt_confirmation
 
-    if destination is None:
-        # TODO: Choose a sensible system-dependent path.
-        destination = Path.cwd()
+    print = get_console().print
+
+    def make_config_path(value: str) -> Path:
+        path = Path(value.strip())
+        if not path.is_absolute():
+            path = path.resolve()
+        check_config_path(path)
+        return path
+
+    def make_device_name(value: str) -> str:
+        device_name = value.strip()
+        check_device_name(device_name)
+        return device_name
+
+    def make_local_repository_path(value: str) -> Path:
+        path = Path(value)
+        if not path.is_absolute():
+            path = path.resolve()
+        check_local_repository_path(path)
+        return path
 
     if interactive:
-        name = input(f"Repository name: (default to {name})\n").strip() or name
-        destination = Path(input(f"Destination: (default to {destination})\n").strip()) or destination
-    if not destination.is_absolute():
-        destination = Path.cwd() / destination
+        config_path = prompt("Bsv configuration file", make_config_path, default=config_path)
+        device_name = prompt("Device name", make_device_name, default=device_name)
+        local_repository_path = prompt("Destination", make_local_repository_path, default=local_repository_path)
 
-    if not name:
-        raise RuntimeError("repository name cannot be empty")
-    if not destination.parent.exists():
-        raise RuntimeError(f"destination directory {destination.parent} does not exists")
-    if destination.exists() and not destination.is_dir():
-        raise RuntimeError(f"destination {destination} exists but is not a directory")
-    if destination.exists() and len(list(destination.iterdir())):
-        raise RuntimeError(f"destination directory {destination} is not empty")
+    if not config_path.is_absolute():
+        config_path = config_path.resolve()
+    if not local_repository_path.is_absolute():
+        local_repository_path = local_repository_path.resolve()
 
     try:
-        destination.mkdir(exist_ok=True)
-    except:
-        raise RuntimeError(f"failed to create destination directory {destination}")
+        check_config_path(config_path)
+        check_device_name(device_name)
+        check_local_repository_path(local_repository_path)
+    except ValueError as err:
+        get_error_console().print(err, style="bold red")
+        return 1
 
-    bsv_table = tomlkit.table()
-    bsv_table.add(tomlkit.comment("Name of the repository."))
-    bsv_table.add(tomlkit.comment("Ideally, this should be unique among all connected repositories."))
-    bsv_table.add("name", name)
-    bsv_table.add(tomlkit.nl())
-    bsv_table.add(tomlkit.comment("Mapping between bsv tree and the actual filesystem."))
-    bsv_table.add("path_map", tomlkit.array())
+    print("Bsv repository will be created with the following settings:", style="green")
+    print("")
+    print(f"\t[blue]:page_facing_up: Config path[/blue]:      [bold yellow]{config_path}")
+    print(f"\t[blue]:computer: Device name[/blue]:      [bold yellow]{device_name}")
+    print(f"\t[blue]:floppy_disk: Local repository[/blue]: [bold yellow]{local_repository_path}")
+    print("")
 
-    cas_table = tomlkit.table()
-    cas_table.add("type", "simple")
-    cas_table.add("hash", "sha256")
+    if interactive:
+        if not prompt_confirmation("Create repository ?"):
+            return 1
 
-    doc = tomlkit.document()
-    doc.add(tomlkit.comment("bsv repository configuration"))
-    doc.add(tomlkit.comment(f"Created by {getlogin()} on {DateTime.now().isoformat()}."))
-    doc.add(tomlkit.nl())
-    doc.add("bsv", bsv_table)
-    doc.add(tomlkit.nl())
-    doc.add("cas", cas_table)
-
-    config_path = destination / "bsv_config.toml"
-    try:
-        stream = config_path.open("w", encoding="utf-8")
-    except:
-        raise RuntimeError("failed to open configuration file {config_path}")
-
-    with stream:
-        tomlkit.dump(doc, stream)
+    create_repository(
+        config_path = config_path,
+        device_name = device_name,
+        local_repository_path = local_repository_path,
+    )
 
     return 0

src/bsv/exception.py

@@ -0,0 +1,32 @@
+# bsv - Backup, Synchronization, Versioning
+# Copyright (C) 2023  Simon Boyé
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from __future__ import annotations
+
+
+class BsvError(RuntimeError):
+    pass
+
+class NotFound(BsvError):
+    pass
+
+class UnmappedPath(BsvError):
+    pass
+
+class UnexpectedObjectType(BsvError):
+    pass
+
+class ConfigError(BsvError):
+    pass

src/bsv/main.py

@@ -22,7 +22,9 @@ import sys
 from textwrap import dedent
 
 from bsv import __version__
+from bsv.cli import get_error_console, init_consoles
 from bsv.command import init_commands
+from bsv.util import default_bsv_config_path
 
 
 def make_parser(
@@ -31,10 +33,20 @@ def make_parser(
 ) -> ArgumentParser:
     parent_parser = ArgumentParser(add_help=False)
     parent_parser.add_argument(
-        "--repository",
-        type = Path,
+        "--color",
+        default = "auto",
+        choices = ("always", "auto", "never"),
         help = dedent("""
-            Bsv repository path. Overides default paths and BSV_REPOSITORY environment variable.
+            Force or disable colors, or auto-detect terminal support.
+        """).strip(),
+    )
+    parent_parser.add_argument(
+        "--config",
+        default = default_bsv_config_path(),
+        type = Path,
+        dest = "config_path",
+        help = dedent("""
+            Bsv config path. Overrides default paths and BSV_CONFIG environment variable.
         """).strip(),
     )
 
@@ -68,16 +80,16 @@ def main(
     )
     arg_dict = vars(parser.parse_args(args or sys.argv[1:]))
 
-    repository_path: Path | None = arg_dict.pop("repository")
-    if repository_path is None and "BSV_REPOSITORY" in os.environ:
-        repository_path = Path(os.environ["BSV_REPOSITORY"])
-    # else:
-    #     for path in get_config_dirs():
-    #         maybe_config_path = path / "config.toml"
-    #         if maybe_config_path.is_file():
-    #             config_path = maybe_config_path
-    #             break
+    color = arg_dict.pop("color")
+    init_consoles(color=color)
 
     command = arg_dict.pop("command")
 
-    return command(repository_path=repository_path, **arg_dict)
+    try:
+        return command(**arg_dict)
+    except Exception as err:
+        get_error_console().print_exception()
+    except KeyboardInterrupt:
+        return 130
+
+    return 0

src/bsv/object.py

@@ -15,33 +15,30 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 from __future__ import annotations
 
-from abc import ABC, abstractmethod
-from typing import BinaryIO
+from dataclasses import dataclass
 
 
-def read_exact(stream: BinaryIO, num_bytes: int) -> bytes:
-    data = stream.read(num_bytes)
-    if len(data) != num_bytes:
-        raise IOError(f"expected {num_bytes} bytes, got {len(data)}")
-    return data
+@dataclass(frozen=True, order=True, slots=True)
+class Digest:
+    digest: bytes = b""
 
-def read_exact_or_eof(stream: BinaryIO, num_bytes: int) -> bytes | None:
-    data = stream.read(num_bytes)
-    if not data:
-        return None
-    if len(data) != num_bytes:
-        raise IOError(f"expected {num_bytes} bytes, got {len(data)}")
-    return data
+    def __bool__(self) -> bool:
+        return bool(self.digest)
+
+    def __repr__(self) -> str:
+        return self.digest.hex()
 
 
-class Hash(ABC):
-    name: str
-    digest_size: int
+@dataclass(frozen=True, order=True, slots=True)
+class ObjectInfo:
+    digest: Digest
+    object_type: bytes
+    size: int
 
-    @abstractmethod
-    def update(self, *data: bytes | bytearray | memoryview):
-        ...
+    def __repr__(self) -> str:
+        return f"<{self.__class__.__name__} {self.digest} {self.object_type.decode()} {self.size}B>"
 
-    @abstractmethod
-    def digest(self) -> bytes:
-        ...
+
+@dataclass(frozen=True, order=True, slots=True)
+class Object(ObjectInfo):
+    data: bytes

src/bsv/path_map.py

@@ -0,0 +1,89 @@
+# bsv - Backup, Synchronization, Versioning
+# Copyright (C) 2023  Simon Boyé
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from __future__ import annotations
+from dataclasses import dataclass
+from itertools import pairwise
+
+from pathlib import Path, PurePosixPath
+from typing import Any
+
+from bsv.exception import UnmappedPath
+
+
+@dataclass(order=True, frozen=True, slots=True)
+class PathPair:
+    bsv: PurePosixPath
+    fs: Path
+
+    def __post_init__(self):
+        if not self.bsv.is_absolute() or not self.fs.is_absolute():
+            raise ValueError("paths in path_map must be absolute")
+        super().__setattr__("fs", self.fs.resolve())
+
+    @classmethod
+    def from_obj(cls, obj: dict[str, str]) -> PathPair:
+        return cls(
+            bsv = PurePosixPath(obj["bsv"]),
+            fs = Path(obj["fs"]),
+        )
+
+
+class PathMap:
+    pairs: list[PathPair]
+
+    def __init__(self, pairs: list[PathPair]=[]):
+        self.pairs = sorted(pairs)
+        for path0, path1 in pairwise(self.pairs):
+            if path0 == path1 or path1.bsv.relative_to(path0.bsv):
+                raise ValueError("bsv paths must be unique and independent")
+
+    @classmethod
+    def from_obj(cls, obj: list[dict[str, str]]) -> PathMap:
+        return cls([
+            PathPair.from_obj(item)
+            for item in obj
+        ])
+
+    def mount_point(self, fs_path: Path) -> PathPair:
+        fs_path = fs_path.resolve()
+        best_pair = None
+        best_relative = None
+        for pair in self.pairs:
+            try:
+                relative = fs_path.relative_to(pair.fs)
+                if not best_pair or not best_relative or len(relative.parts) < len(best_relative.parts):
+                    best_pair = pair
+                    best_relative = relative
+            except ValueError:
+                pass
+        if best_pair is None:
+            raise UnmappedPath(f"unmapped fs path {fs_path}")
+        return best_pair
+
+    def relative_bsv_path(self, fs_target: Path, relative_to: Path) -> PurePosixPath:
+        if not relative_to.is_absolute():
+            relative_to = fs_target / relative_to
+
+        fs_target = fs_target.resolve()
+        relative_to = relative_to.resolve()
+
+        target_mount_point = self.mount_point(fs_target)
+        base_mount_point = self.mount_point(relative_to)
+
+        raise NotImplemented("not implemented yet")
+
+    def clone(self) -> PathMap:
+        return PathMap(self.pairs)

src/bsv/repository.py

@@ -16,21 +16,25 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
-from datetime import UTC, datetime as DateTime, timedelta as TimeDelta
+from datetime import datetime as DateTime
 import hashlib
 from io import BytesIO
 from pathlib import Path, PurePosixPath
-import platform
 import tomllib
-from typing import Any, BinaryIO, Callable, Type
+from typing import TYPE_CHECKING, Any, BinaryIO, Self
 
 from fastcdc import fastcdc
-import tomlkit
 
 from bsv import __version__
+from bsv.exception import ConfigError
+from bsv.object import ObjectInfo
+from bsv.path_map import PathMap
 from bsv.simple_cas import SimpleCas
-from bsv.simple_cas.cas import ConfigError, Digest, SimpleCas
-from bsv.simple_cas.util import Hash, read_exact, read_exact_or_eof
+from bsv.simple_cas.cas import Digest, SimpleCas
+from bsv.util import default_bsv_config_path, default_local_repository_path, read_exact, read_exact_or_eof, time_from_timestamp_us, timestamp_us_from_time
+
+if TYPE_CHECKING:
+    from bsv.tree_walker import TreeWalker
 
 
 DEFAULT_MIN_CHUNK_SIZE = 1 << 12
@@ -39,91 +43,191 @@ DEFAULT_MAX_CHUNK_SIZE = 1 << 20
 
 
 class Repository:
-    _path: Path
-    _name: str
+    _config_path: Path
+    _device_name: str
+    _local_repository_path: Path
 
     _cas: SimpleCas
     _min_chunk_size: int = DEFAULT_MIN_CHUNK_SIZE
     _avg_chunk_size: int = DEFAULT_AVG_CHUNK_SIZE
     _max_chunk_size: int = DEFAULT_MAX_CHUNK_SIZE
 
-    _path_map: list[PathPair]
+    _path_map: PathMap
     # _remotes: list[object]
 
     _context_depth: int = 0
 
-    def __init__(self, path: Path):
-        self._path = path
+    def __init__(self, config_path: Path):
+        self._config_path = config_path.resolve()
 
-        with self.config_file.open("rb") as stream:
+        with self._config_path.open("rb") as stream:
             config = tomllib.load(stream)
 
         bsv = config.get("bsv", {})
+        def get(key: str) -> Any:
+            value = bsv.get(key)
+            if value is None:
+                raise ConfigError(f"invalid bsv configuration: missing bsv.{key} item")
+            return value
 
-        self._name = bsv.get("name") or platform.node()
+        self._device_name = get("device_name")
+        self._local_repository_path = Path(get("local_repository"))
+        self._min_chunk_size = get("min_chunk_size")
+        self._avg_chunk_size = get("avg_chunk_size")
+        self._max_chunk_size = get("max_chunk_size")
+        self._path_map = PathMap.from_obj(get("path_map"))
 
-        self._cas = make_cas(
-            bsv.get("cas"),
-            self._path,
-            lambda: hashlib.new(bsv.get("hash")), # type: ignore
+        self._cas = make_cas(self._local_repository_path)
+
+
+    @property
+    def config_path(self) -> Path:
+        return self._config_path
+
+    @property
+    def device_name(self) -> str:
+        return self._device_name
+
+    @property
+    def path_map(self) -> PathMap:
+        return self._path_map.clone()
+
+    def get_blob(self, digest: Digest) -> BlobObject:
+        with self:
+            obj, blob = self._read(digest, object_type=b"blob")
+            return BlobObject(
+                digest = obj.digest,
+                object_type = obj.object_type,
+                size = obj.size,
+                blob = blob,
+            )
+
+    def add_blob(self, stream: BinaryIO, *, dry_run: bool=False) -> BlobObject:
+        with self:
+            return self._write(b"blob", stream, dry_run=dry_run)
+
+    def get_symlink(self, digest: Digest) -> SymlinkObject:
+        with self:
+            obj = self._cas.read(digest, object_type=b"slnk")
+            return SymlinkObject(
+                digest = obj.digest,
+                object_type = obj.object_type,
+                size = obj.size,
+                symlink = Symlink.from_bytes(self, obj.data),
+            )
+
+    def add_symlink(self, symlink: Symlink, *, dry_run: bool=False) -> SymlinkObject:
+        with self:
+            data = symlink.to_bytes()
+            return SymlinkObject(
+                digest = self._cas.write(b"slnk", data, dry_run=dry_run),
+                object_type = b"slnk",
+                size = len(data),
+                symlink = symlink,
+            )
+
+    def add_symlink_from_fs_target(self, fs_symlink: Path, fs_target: Path, *, dry_run: bool=False) -> SymlinkObject:
+        assert fs_symlink.is_absolute()
+        return self.add_symlink(
+            Symlink(
+                repo = self,
+                is_absolute = fs_target.is_absolute(),
+                target = self._path_map.relative_bsv_path(fs_target, relative_to=fs_symlink),
+            ),
+            dry_run = dry_run,
         )
-        self._min_chunk_size = bsv.get("min_chunk_size")
-        self._avg_chunk_size = bsv.get("avg_chunk_size")
-        self._max_chunk_size = bsv.get("max_chunk_size")
 
-        self._path_map = [
-            PathPair.from_obj(pair)
-            for pair in bsv.get("path_map", [])
-        ]
-
-    @property
-    def path(self) -> Path:
-        return self._path
-
-    @property
-    def config_file(self) -> Path:
-        return self.path / "bsv_config.toml"
-
-    @property
-    def name(self) -> str:
-        return self._name
-
-    @property
-    def path_map(self) -> list[PathPair]:
-        return list(self._path_map)
-
-    def get_blob(self, digest: Digest) -> Blob:
+    def get_tree(self, digest: Digest) -> TreeObject:
         with self:
-            return self._read(digest, object_type=b"blob", cls=Blob) # type: ignore
+            obj = self._cas.read(digest, object_type=b"tree")
+            return TreeObject(
+                digest = obj.digest,
+                object_type = obj.object_type,
+                size = obj.size,
+                tree = Tree.from_bytes(self, obj.data),
+            )
 
-    def add_blob(self, stream: BinaryIO) -> Digest:
+    def add_tree(self, tree: Tree, *, dry_run: bool=False) -> TreeObject:
         with self:
-            return self._write(b"blob", stream)
+            data = tree.to_bytes()
+            return TreeObject(
+                digest = self._cas.write(b"tree", data, dry_run=dry_run),
+                object_type = b"tree",
+                size = len(data),
+                tree = tree,
+            )
 
-    def get_tree(self, digest: Digest) -> Tree:
+    def add_tree_from_path(self, path: Path, *, dry_run: bool=False) -> TreeObject:
+        from bsv.tree_walker import TreeWalker
+        walker = TreeWalker(self, dry_run=dry_run)
+        return walker.add_tree(path)
+
+    def get_snapshot(self, digest: Digest) -> SnapshotObject:
         with self:
-            return Tree.from_bytes(self, self._cas.read(digest, object_type=b"tree").data)
+            obj = self._cas.read(digest, object_type=b"snap")
+            return SnapshotObject(
+                digest = obj.digest,
+                object_type = obj.object_type,
+                size = obj.size,
+                snapshot = Snapshot.from_bytes(self, obj.data),
+            )
 
-    def add_tree(self, tree: Tree) -> Digest:
+    def add_snapshot(self, snapshot: Snapshot, *, dry_run: bool=False) -> SnapshotObject:
         with self:
-            return self._cas.write(b"tree", tree.to_bytes())
+            data = snapshot.to_bytes()
+            return SnapshotObject(
+                digest = self._cas.write(b"snap", data, dry_run=dry_run),
+                object_type = b"snap",
+                size = len(data),
+                snapshot = snapshot,
+            )
 
-    def get_snapshot(self, digest: Digest) -> Snapshot:
-        with self:
-            return Snapshot.from_bytes(self, self._cas.read(digest, object_type=b"snap").data)
+    # def take_snapshot(
+    #     self,
+    #     parent_digests: list[Digest] = [],
+    #     *,
+    #     walker_type: Type[TreeWalker] | None = None,
+    #     dry_run: bool = False,
+    # ):
+    #     from bsv.tree_walker import TreeWalker
 
-    def add_snapshot(self, snapshot: Snapshot) -> Digest:
-        with self:
-            return self._cas.write(b"snap", snapshot.to_bytes())
+    #     walker = (walker_type or TreeWalker)(self, dry_run=dry_run)
 
-    def _read(self, digest: Digest, object_type: bytes, cls: Type[ChunkedObject]) -> ChunkedObject:
+    #     # parents = [
+    #     #     self.get_snapshot(digest)
+    #     #     for digest in parent_digests
+    #     # ]
+    #     parent = self.get_snapshot(parent_digests[0]) if parent_digests else None
+
+    #     snapshot = Snapshot(
+    #         repo = self,
+    #         tree_digest = walker.add_virtual_tree(self._path_map, parent=),
+    #         parents = parent_digests,
+    #         repo_name = self._name,
+    #         timestamp = timestamp_us_from_time(DateTime.now()),
+    #     )
+    #     return self.add_snapshot(snapshot, dry_run=dry_run)
+
+
+    def get_ref(self, key: str) -> Digest | None:
+        return self._cas.get_ref(key)
+
+    def set_ref(self, key: str, digest: Digest):
+        self._cas.set_ref(key, digest)
+
+    def get_head_snapshot(self) -> Digest | None:
+        return self.get_ref("HEAD")
+
+
+    def _read(self, digest: Digest, object_type: bytes) -> tuple[ObjectInfo, Blob]:
         obj = self._cas.read(digest, object_type=object_type)
         stream = BytesIO(obj.data)
-        return cls.from_stream(self, stream, digest_size=self._cas._digest_size)
+        return obj, Blob.from_stream(self, stream, digest_size=self._cas._digest_size)
 
-    def _write(self, object_type: bytes, stream: BinaryIO) -> Digest:
+    def _write(self, object_type: bytes, stream: BinaryIO, *, dry_run: bool=False) -> BlobObject:
         out = BytesIO()
         size = 0
+        chunks = []
         for chunk in fastcdc(
             stream,
             min_size = self._min_chunk_size,
@@ -132,10 +236,20 @@ class Repository:
             fat = True,
         ):
             size += chunk.length
-            digest = self._cas.write(b"chnk", chunk.data)
+            digest = self._cas.write(b"chnk", chunk.data, dry_run=dry_run)
+            chunks.append(Chunk(digest, chunk.length))
             out.write(digest.digest)
             out.write(chunk.length.to_bytes(4))
-        return self._cas.write(object_type, size.to_bytes(8) + out.getvalue())
+        return BlobObject(
+            digest = self._cas.write(object_type, size.to_bytes(8) + out.getvalue()),
+            object_type = object_type,
+            size = 8 + len(out.getvalue()),
+            blob = Blob(
+                repo = self,
+                size = size,
+                chunks = chunks,
+            )
+        )
 
     def __enter__(self):
         if self._context_depth == 0:
@@ -149,9 +263,30 @@ class Repository:
             return self._cas.__exit__(exc_type, exc_value, traceback)
 
 
+def check_config_path(path: Path):
+    if path.exists():
+        raise ValueError(f"{path} already exists.")
+    if path != default_bsv_config_path() and not path.parent.is_dir():
+        raise ValueError(f"{path.parent} does not exist or is not a directory.")
+
+def check_device_name(device_name: str):
+    if not device_name:
+        raise ValueError("Device name cannot be empty.")
+    if not device_name.isidentifier():
+        raise ValueError(f"{device_name} is not a valid device name.")
+
+def check_local_repository_path(path: Path):
+    if path != default_local_repository_path() and not path.parent.exists():
+        raise ValueError(f"Directory {path.parent} does not exists.")
+    if path.exists() and not path.is_dir():
+        raise ValueError(f"{path} exists but is not a directory.")
+    if path.exists() and len(list(path.iterdir())):
+        raise ValueError(f"Local repository directory {path} is not empty.")
+
 def create_repository(
-    destination: Path,
-    name: str,
+    config_path: Path,
+    device_name: str,
+    local_repository_path: Path,
     cas: str = "simple",
     hash: str = "sha256",
     min_chunk_size: int = DEFAULT_MIN_CHUNK_SIZE,
@@ -161,65 +296,108 @@ def create_repository(
     from datetime import datetime as DateTime
     from os import getlogin
 
-    if not name:
-        raise RuntimeError("repository name cannot be empty")
-    if not destination.parent.exists():
-        raise RuntimeError(f"destination directory {destination.parent} does not exists")
-    if destination.exists() and not destination.is_dir():
-        raise RuntimeError(f"destination {destination} exists but is not a directory")
-    if destination.exists() and len(list(destination.iterdir())):
-        raise RuntimeError(f"destination directory {destination} is not empty")
+    import tomlkit
+
+    check_config_path(config_path)
+    check_device_name(device_name)
+    check_local_repository_path(local_repository_path)
+
+    if config_path == default_bsv_config_path():
+        try:
+            config_path.parent.mkdir(parents=True, exist_ok=True)
+        except:
+            raise RuntimeError(f"failed to create bsv config destination directory {config_path.parent}")
 
     try:
-        destination.mkdir(exist_ok=True)
+        local_repository_path.mkdir(exist_ok=True)
     except:
-        raise RuntimeError(f"failed to create destination directory {destination}")
+        raise RuntimeError(f"failed to create local repository directory {local_repository_path}")
 
     bsv_table = tomlkit.table()
-    bsv_table.add(tomlkit.comment("Name of the repository."))
-    bsv_table.add(tomlkit.comment("Ideally, this should be unique among all connected repositories."))
-    bsv_table.add("name", name)
+
+    bsv_table.add(tomlkit.comment("Name of the instance."))
+    bsv_table.add(tomlkit.comment("Ideally, this should be unique among all connected devices."))
+    bsv_table.add("device_name", device_name)
+
     bsv_table.add(tomlkit.nl())
-    bsv_table.add(tomlkit.comment("Mapping between bsv tree and the actual filesystem."))
-    bsv_table.add("path_map", tomlkit.array())
-    bsv_table.add("cas", cas)
-    bsv_table.add("hash", hash)
+    bsv_table.add(tomlkit.comment("Path to the local repository."))
+    bsv_table.add("local_repository", str(local_repository_path))
+
+    bsv_table.add(tomlkit.nl())
+    bsv_table.add(tomlkit.comment("Properties of the content-based chunking algorithm."))
     bsv_table.add("min_chunk_size", min_chunk_size)
     bsv_table.add("avg_chunk_size", avg_chunk_size)
     bsv_table.add("max_chunk_size", max_chunk_size)
 
-    doc = tomlkit.document()
-    doc.add(tomlkit.comment("bsv repository configuration"))
-    doc.add(tomlkit.comment(f"Created by {getlogin()} on {DateTime.now().isoformat()}."))
-    doc.add(tomlkit.nl())
-    doc.add("bsv", bsv_table)
+    bsv_table.add(tomlkit.nl())
+    bsv_table.add(tomlkit.comment("Mapping between bsv tree and the local filesystem."))
+    bsv_table.add("path_map", tomlkit.array())
+
+    bsv_config = tomlkit.document()
+    bsv_config.add(tomlkit.comment("bsv device configuration"))
+    bsv_config.add(tomlkit.comment(f"Created by {getlogin()} on {DateTime.now().isoformat()}."))
+    bsv_config.add(tomlkit.nl())
+    bsv_config.add("bsv", bsv_table)
+
+
+    cas_table = tomlkit.table()
+    cas_table.add("type", cas)
+    cas_table.add("hash", hash)
+
+    cas_config = tomlkit.document()
+    cas_config.add(tomlkit.comment(f"bsv local repository configuration for instance {config_path}."))
+    cas_config.add(tomlkit.comment(f"Created by {getlogin()} on {DateTime.now().isoformat()}."))
+    cas_config.add(tomlkit.nl())
+    cas_config.add("cas", cas_table)
 
-    config_path = destination / "bsv_config.toml"
     try:
-        stream = config_path.open("w", encoding="utf-8")
+        bsv_stream = config_path.open("w", encoding="utf-8")
     except:
-        raise RuntimeError("failed to open configuration file {config_path}")
+        raise RuntimeError(f"failed to open bsv configuration file {config_path}")
+    try:
+        cas_stream = (local_repository_path / "bsv_repository.config").open("w", encoding="utf-8")
+    except:
+        raise RuntimeError(f"failed to open local repository configuration file {config_path}")
 
-    with stream:
-        tomlkit.dump(doc, stream)
+    with bsv_stream:
+        tomlkit.dump(bsv_config, bsv_stream)
 
-    return Repository(destination)
+    with cas_stream:
+        tomlkit.dump(cas_config, cas_stream)
+
+    repo = Repository(config_path)
+
+    return repo
 
 
-def make_cas(cas_name: str, path: Path, hash_factory: Callable[[], Hash]) -> SimpleCas:
-    if cas_name == "simple":
-        return SimpleCas(path, hash_factory)
-    raise ConfigError(f"unknown cas name {cas_name}")
+def make_cas(cas_config_path: Path) -> SimpleCas:
+    with (cas_config_path / "bsv_repository.config").open("rb") as stream:
+        config = tomllib.load(stream)
+
+    cas = config.get("cas", {})
+    def get(key: str) -> Any:
+        value = cas.get(key)
+        if value is None:
+            raise ConfigError(f"invalid repository configuration: missing {key} item")
+        return value
+
+    type = get("type")
+    hash_factory = lambda: hashlib.new(get("hash"))
+    if type == "simple":
+        return SimpleCas(cas_config_path, hash_factory) # type: ignore
+    raise ConfigError(f"unknown cas type {type}")
 
 
-@dataclass
+
+
+@dataclass(slots=True)
 class ChunkedObject:
     repo: Repository
     size: int
     chunks: list[Chunk]
 
     @classmethod
-    def from_stream(cls, repo: Repository, stream: BinaryIO, digest_size: int) -> ChunkedObject:
+    def from_stream(cls, repo: Repository, stream: BinaryIO, digest_size: int) -> Self:
         self = cls(
             repo = repo,
             size = int.from_bytes(read_exact(stream, 8)),
@@ -229,16 +407,41 @@ class ChunkedObject:
             self.chunks.append(chunk)
         return self
 
+    def reader(self) -> ChunkedObjectReader:
+        return ChunkedObjectReader(self)
 
-@dataclass
-class Blob(ChunkedObject):
+
+@dataclass(frozen=True, slots=True)
+class Chunk:
+    digest: Digest
+    size: int
+
+    @classmethod
+    def from_stream(cls, stream: BinaryIO, digest_size: int) -> Self | None:
+        digest_bytes = read_exact_or_eof(stream, digest_size)
+        if digest_bytes is None:
+            return None
+        digest = Digest(digest_bytes)
+
+        return cls(
+            digest = digest,
+            size = int.from_bytes(read_exact(stream, 4)),
+        )
+
+
+class ChunkedObjectReader:
+    _chunked_object: ChunkedObject
     _chunk_index: int = 0
     _chunk_data: bytes = b""
 
+    def __init__(self, chunked_object: ChunkedObject):
+        self._chunked_object = chunked_object
+
     def read(self, num_bytes: int = -1) -> bytes:
+        chunks = self._chunked_object.chunks
         parts = [self._chunk_data]
         size = len(parts[-1])
-        while (num_bytes < 0 or size < num_bytes) and self._chunk_index < len(self.chunks):
+        while (num_bytes < 0 or size < num_bytes) and self._chunk_index < len(chunks):
             parts.append(self.read1())
             size += len(parts[-1])
         if num_bytes >= 0:
@@ -248,27 +451,79 @@ class Blob(ChunkedObject):
         return b"".join(parts)
 
     def read1(self) -> bytes:
-        if self._chunk_index == len(self.chunks):
+        cas = self._chunked_object.repo._cas
+        chunks = self._chunked_object.chunks
+        if self._chunk_index == len(chunks):
             return b""
-        object = self.repo._cas.read(self.chunks[self._chunk_index].digest, object_type=b"chnk")
+        object = cas.read(chunks[self._chunk_index].digest, object_type=b"chnk")
         self._chunk_index += 1
         return object.data
 
 
+
+@dataclass(slots=True)
+class Blob(ChunkedObject):
+    pass
+
+@dataclass(frozen=True, order=True, slots=True)
+class BlobObject(ObjectInfo):
+    blob: Blob
+
+
+@dataclass(slots=True)
+class Symlink:
+    repo: Repository
+    is_absolute: bool
+    target: PurePosixPath
+
+    @classmethod
+    def from_stream(cls, repo: Repository, stream: BinaryIO) -> Self:
+        return cls(
+            repo = repo,
+            is_absolute = bool(read_exact(stream, 1)),
+            target = PurePosixPath(stream.read().decode("utf-8")),
+        )
+
+    @classmethod
+    def from_bytes(cls, repo: Repository, bytes: bytes) -> Self:
+        stream = BytesIO(bytes)
+        return cls.from_stream(repo, stream)
+
+    def write(self, stream: BinaryIO):
+        stream.write(self.is_absolute.to_bytes(1))
+        stream.write(self.target.as_posix().encode("utf-8"))
+
+    def to_bytes(self) -> bytes:
+        stream = BytesIO()
+        self.write(stream)
+        return stream.getvalue()
+
+@dataclass(frozen=True, order=True, slots=True)
+class SymlinkObject(ObjectInfo):
+    symlink: Symlink
+
+
 @dataclass
 class Tree:
     repo: Repository
     items: list[TreeItem]
 
+    @property
+    def total_size(self) -> int:
+        return sum(
+            item.size
+            for item in self.items
+        )
+
     @classmethod
-    def from_stream(cls, repo: Repository, stream: BinaryIO) -> Tree:
+    def from_stream(cls, repo: Repository, stream: BinaryIO) -> Self:
         tree = Tree(repo, [])
         while (item := TreeItem.from_stream(stream, repo._cas._digest_size)) is not None:
             tree.items.append(item)
         return tree
 
     @classmethod
-    def from_bytes(cls, repo: Repository, data: bytes) -> Tree:
+    def from_bytes(cls, repo: Repository, data: bytes) -> Self:
         stream = BytesIO(data)
         return cls.from_stream(repo, stream)
 
@@ -282,156 +537,143 @@ class Tree:
         self.write(stream)
         return stream.getvalue()
 
+    def __len__(self) -> int:
+        return len(self.items)
+
+    def get(self, key: str) -> TreeItem | None:
+        for item in self.items:
+            if item.name == key:
+                return item
+        return None
+
+    def __getitem__(self, key: str) -> TreeItem:
+        item = self.get(key)
+        if item is None:
+            raise KeyError(f"{key} not found")
+        return item
+
+@dataclass(frozen=True, order=True, slots=True)
+class TreeObject(ObjectInfo):
+    tree: Tree
+
+    @property
+    def total_size(self) -> int:
+        return self.size + self.tree.total_size
 
-EPOCH = DateTime(1970, 1, 1, tzinfo=UTC)
 
 @dataclass
 class TreeItem:
-    name: str
     digest: Digest
+    object_type: bytes
+    size: int
     permissions: int
-    creation_timestamp: int
-    modification_timestamp: int
+    modification_timestamp_us: int
+    name: str
 
     def __init__(
         self,
-        name: str,
         digest: Digest,
+        object_type: bytes,
+        size: int,
         permissions: int,
-        creation_timestamp: int,
-        modification_timestamp: int,
+        modification_timestamp_us: int,
+        name: str,
     ):
         if "/\\" in name:
             raise ValueError(f"invalid tree item name {name}")
-        self.name = name
         self.digest = digest
+        self.object_type = object_type
+        self.size = size
         self.permissions = permissions
-        self.creation_timestamp = creation_timestamp
-        self.modification_timestamp = modification_timestamp
-
-    @property
-    def creation_time(self) -> DateTime:
-        return time_from_timestamp(self.creation_timestamp)
-    @creation_time.setter
-    def creation_time(self, time: DateTime):
-        self.creation_timestamp = timestamp_from_time(time)
+        self.modification_timestamp_us = modification_timestamp_us
+        self.name = name
 
     @property
     def modification_time(self) -> DateTime:
-        return time_from_timestamp(self.modification_timestamp)
+        return time_from_timestamp_us(self.modification_timestamp_us)
     @modification_time.setter
     def modification_time(self, time: DateTime):
-        self.modification_timestamp = timestamp_from_time(time)
+        self.modification_timestamp_us = timestamp_us_from_time(time)
 
     @classmethod
-    def from_stream(cls, stream: BinaryIO, digest_size: int) -> TreeItem | None:
+    def from_stream(cls, stream: BinaryIO, digest_size: int) -> Self | None:
         digest_bytes = read_exact_or_eof(stream, digest_size)
         if digest_bytes is None:
             return None
         return TreeItem(
             digest = Digest(digest_bytes),
+            object_type = read_exact(stream, 4),
+            size = int.from_bytes(read_exact(stream, 8)),
             permissions = int.from_bytes(read_exact(stream, 2)),
-            creation_timestamp = int.from_bytes(read_exact(stream, 8), signed=True),
-            modification_timestamp = int.from_bytes(read_exact(stream, 8), signed=True),
+            modification_timestamp_us = int.from_bytes(read_exact(stream, 8), signed=True),
             name = read_exact(stream, int.from_bytes(read_exact(stream, 2))).decode("utf-8"),
         )
 
     def write(self, stream: BinaryIO):
         stream.write(self.digest.digest)
+        stream.write(self.object_type)
+        stream.write(self.size.to_bytes(8))
         stream.write(self.permissions.to_bytes(2))
-        stream.write(self.creation_timestamp.to_bytes(8, signed=True))
-        stream.write(self.modification_timestamp.to_bytes(8, signed=True))
+        stream.write(self.modification_timestamp_us.to_bytes(8, signed=True))
         name_bytes = self.name.encode("utf-8")
         stream.write(len(name_bytes).to_bytes(2))
         stream.write(name_bytes)
 
 
+
+
 @dataclass
 class Snapshot:
     repo: Repository
     tree_digest: Digest
+    parents: list[Digest]
     repo_name: str
-    timestamp: int
+    timestamp_us: int
+
+    def __post_init__(self):
+        assert len(self.parents) < 256
 
     @property
     def time(self) -> DateTime:
-        return time_from_timestamp(self.timestamp)
+        return time_from_timestamp_us(self.timestamp_us)
     @time.setter
     def time(self, time: DateTime):
-        self.timestamp = timestamp_from_time(time)
+        self.timestamp_us = timestamp_us_from_time(time)
 
     @classmethod
-    def from_stream(cls, repo: Repository, stream: BinaryIO) -> Snapshot:
+    def from_stream(cls, repo: Repository, stream: BinaryIO) -> Self:
         return Snapshot(
             repo = repo,
             tree_digest = Digest(read_exact(stream, repo._cas._digest_size)),
+            parents = [
+                Digest(read_exact(stream, repo._cas._digest_size))
+                for _ in range(int.from_bytes(read_exact(stream, 1)))
+            ],
             repo_name = read_exact(stream, int.from_bytes(read_exact(stream, 2))).decode("utf-8"),
-            timestamp = int.from_bytes(read_exact(stream, 8), signed=True),
+            timestamp_us = int.from_bytes(read_exact(stream, 8), signed=True),
         )
 
     @classmethod
-    def from_bytes(cls, repo: Repository, data: bytes) -> Snapshot:
+    def from_bytes(cls, repo: Repository, data: bytes) -> Self:
         stream = BytesIO(data)
         return cls.from_stream(repo, stream)
 
     def write(self, stream: BinaryIO):
+        assert len(self.parents) < 256
         stream.write(self.tree_digest.digest)
+        stream.write(len(self.parents).to_bytes(1))
+        for parent in self.parents:
+            stream.write(parent.digest)
         repo_name_bytes = self.repo_name.encode("utf-8")
         stream.write(len(repo_name_bytes).to_bytes(2))
         stream.write(repo_name_bytes)
-        stream.write(self.timestamp.to_bytes(8, signed=True))
+        stream.write(self.timestamp_us.to_bytes(8, signed=True))
 
     def to_bytes(self) -> bytes:
         stream = BytesIO()
         self.write(stream)
         return stream.getvalue()
 
-
-@dataclass
-class Chunk:
-    digest: Digest
-    size: int
-
-    @classmethod
-    def from_stream(cls, stream: BinaryIO, digest_size: int) -> Chunk | None:
-        digest_bytes = read_exact_or_eof(stream, digest_size)
-        if digest_bytes is None:
-            return None
-        digest = Digest(digest_bytes)
-
-        return cls(
-            digest = digest,
-            size = int.from_bytes(read_exact(stream, 4)),
-        )
-
-
-class PathPair:
-    bsv: PurePosixPath
-    fs: Path
-
-    def __init__(self, bsv: PurePosixPath, fs: Path):
-        self.bsv = bsv
-        self.fs = fs
-
-    @classmethod
-    def from_obj(cls, obj: dict[str, Any]) -> PathPair:
-        bsv = PurePosixPath(obj["bsv"])
-        fs = Path(obj["fs"])
-
-        if not bsv.is_absolute() or not fs.is_absolute():
-            raise ValueError("paths in path_map must be absolute")
-
-        return cls(
-            bsv = obj["bsv"],
-            fs = obj["fs"],
-        )
-
-    def __lt__(self, rhs: PathPair) -> bool:
-        return self.bsv < rhs.bsv
-
-
-def time_from_timestamp(timestamp: int) -> DateTime:
-    return EPOCH + TimeDelta(microseconds=timestamp)
-
-def timestamp_from_time(time: DateTime) -> int:
-    return (time.astimezone(UTC) - EPOCH) // TimeDelta(microseconds=1)
+@dataclass(frozen=True, order=True, slots=True)
+class SnapshotObject(ObjectInfo):
+    snapshot: Snapshot

src/bsv/simple_cas/cas.py

@@ -19,21 +19,10 @@ from dataclasses import dataclass
 import hashlib
 from pathlib import Path
 from typing import Any, BinaryIO, Callable, Iterator
+from bsv.exception import NotFound, UnexpectedObjectType
+from bsv.object import Digest, Object, ObjectInfo
 
-from bsv.simple_cas.util import Hash, read_exact_or_eof
-
-
-class BsvError(RuntimeError):
-    pass
-
-class NotFound(BsvError):
-    pass
-
-class UnexpectedObjectType(BsvError):
-    pass
-
-class ConfigError(BsvError):
-    pass
+from bsv.util import Hash, read_exact_or_eof
 
 
 class SimpleCas:
@@ -105,21 +94,19 @@ class SimpleCas:
             assert size == item.size
             data = stream.read(size)
 
-        return Object(object_type, data)
+        return Object(digest, object_type, size, data)
 
-    def write(self, object_type: bytes, data: bytes) -> Digest:
+    def write(self, object_type: bytes, data: bytes, dry_run: bool=False) -> Digest:
         assert len(object_type) == 4
         assert len(data) < 2**32
 
         hash = self._hash_factory()
         hash.update(object_type)
-        hash.update(b"\0")
         hash.update(len(data).to_bytes(4))
-        hash.update(b"\0")
         hash.update(data)
         digest = Digest(hash.digest())
 
-        if digest not in self:
+        if not dry_run and digest not in self:
             with self._open_writer(digest, object_type, len(data)) as out:
                 out.write(digest.digest)
                 out.write(object_type)
@@ -164,23 +151,7 @@ class SimpleCas:
         return self._root_dir / "refs" / key_path
 
 
-@dataclass(frozen=True, order=True, slots=True)
-class Digest:
-    digest: bytes
-
-    def __repr__(self) -> str:
-        return self.digest.hex()
-
-
-@dataclass
-class Object:
-    object_type: bytes
-    data: bytes
-
-    def __repr__(self) -> str:
-        return f"<Object {self.object_type.decode()}: {len(self.data)}B>"
-
-@dataclass
+@dataclass(frozen=True)
 class IndexItem:
     object_type: bytes
     offset: int
@@ -188,12 +159,3 @@ class IndexItem:
 
     def __repr__(self) -> str:
         return f"<IndexItem {self.object_type.decode()}: {self.offset}B +{self.size}B>"
-
-@dataclass
-class ObjectInfo:
-    digest: Digest
-    object_type: bytes
-    size: int
-
-    def __repr__(self) -> str:
-        return f"<ObjectInfo {self.digest} {self.object_type.decode()} {self.size}B>"

src/bsv/tree_walker.py

@@ -0,0 +1,268 @@
+# bsv - Backup, Synchronization, Versioning
+# Copyright (C) 2023  Simon Boyé
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from __future__ import annotations
+
+from datetime import datetime as DateTime, timedelta as TimeDelta
+from enum import Enum
+from os import stat_result
+from pathlib import Path
+import stat
+
+from bsv.object import Digest, ObjectInfo
+from bsv.repository import BlobObject, Repository, SymlinkObject, Tree, TreeItem, TreeObject
+from bsv.util import is_bsv_repository, object_type_from_mode
+
+
+class Action(Enum):
+    ADD = "add"
+    UPDATE = "update"
+    REMOVE = "remove"
+    IGNORE = "ignore"
+    ERROR = "error"
+
+    @classmethod
+    def from_digests(cls, digest: Digest, source_digest: Digest | None) -> tuple[Action, IgnoreCause | None]:
+        assert digest
+        if not source_digest:
+            return Action.ADD, None
+        elif source_digest == digest:
+            return Action.IGNORE, IgnoreCause.UNCHANGED
+        else:
+            return Action.UPDATE, None
+
+class IgnoreCause(Enum):
+    IGNORE_RULE = "ignore_rule"
+    UNCHANGED = "unchanged"
+    UNSUPPORTED_TYPE = "unsupported_type"
+
+
+class TreeWalker:
+    _repo: Repository
+    _time_rounding_us: int = 2000000
+    _force_hash: bool = False
+    _dry_run: bool = False
+
+    def __init__(
+        self,
+        repo: Repository,
+        *,
+        time_rounding_us: int = 2000000,
+        force_hash: bool = False,
+        dry_run: bool = False,
+    ):
+        self._repo = repo
+        self._time_rounding_us = time_rounding_us
+        self._force_hash = force_hash
+        self._dry_run = dry_run
+
+    # def add_virtual_tree(self, paths: PathMap) -> Digest:
+    #     assert paths
+
+    #     fs_paths = sorted([
+    #         pair.fs
+    #         for pair in paths.pairs
+    #     ])
+
+    #     tree_map = {
+    #         fs_paths[0]: self.add_tree()
+    #     }
+    #     root = {}
+    #     for pair in paths.paths:
+    #         vdir = root
+    #         for part in pair.bsv.parts[:-1]:
+    #             vdir = vdir.setdefault(part, {})
+    #         vdir[pair.bsv.parts[-1]] = pair.fs
+
+    #     return self._add_virtual_tree(root)
+
+    # def _add_virtual_tree(self, vtree: dict[str, dict | Path]) -> Digest:
+    #     tree = Tree(self._repo, [])
+    #     for name, value in vtree.items():
+    #         if isinstance(value, dict):
+    #             digest = self._add_virtual_tree(value)
+    #         elif isinstance(value, Path):
+    #             digest = self.add_tree(value)
+    #         else:
+    #             raise TypeError(f"unexpected type {type(vtree).__name__} for vtree")
+    #         tree.items.append(TreeItem(
+    #             digest = digest,
+    #             object_type = b"tree",
+    #             size = 0,
+    #             permissions = 0o766,
+    #             modification_timestamp = timestamp_us_from_time(DateTime.now()),
+    #             name = name,
+    #         ))
+    #     return self._repo.add_tree(tree, dry_run=self._dry_run)
+
+    def add_tree(self, path: Path, *, source_digest: Digest | None=None) -> TreeObject:
+        pstat = path.stat(follow_symlinks=False)
+        if self.ignore(path, pstat):
+            raise ValueError(f"path {path} is ignored")
+            # self.report(Action.IGNORE, path, pstat, IgnoreCause.IGNORE_RULE)
+            # return Digest()
+        return self._add_tree(path, pstat, source_digest=source_digest)
+
+    def _add_tree(self, path: Path, pstat: stat_result, *, source_digest: Digest | None) -> TreeObject:
+        source = self._repo.get_tree(source_digest).tree if source_digest else None
+
+        tree = Tree(self._repo, [])
+        subpaths = sorted(path.iterdir())
+
+        subpath_index = 0
+        source_item_index = 0
+
+        while subpath_index < len(subpaths) or (source and source_item_index < len(source.items)):
+            subpath = subpaths[subpath_index] if subpath_index < len(subpaths) else None
+            source_item = source.items[source_item_index] if source and source_item_index < len(source.items) else None
+
+            if subpath and source_item:
+                if subpath.name < source_item.name:
+                    source_item = None
+                elif subpath.name > source_item.name:
+                    subpath = None
+
+            if subpath is not None:
+                subpath_index += 1
+            if source_item is not None:
+                source_item_index += 1
+
+            if subpath is not None:
+                obj: ObjectInfo | None = None
+                try:
+                    istat = subpath.lstat()
+
+                    if self.ignore(subpath, istat, source=source_item):
+                        self.report(Action.IGNORE, subpath, istat, IgnoreCause.IGNORE_RULE)
+                        continue
+
+                    if (source_item is not None and
+                        not self._force_hash and
+                        not stat.S_ISDIR(istat.st_mode) and
+                        pstat.st_size == source_item.size and
+                        pstat.st_mtime_ns // (1000 * self._time_rounding_us) == source_item.modification_timestamp_us // self._time_rounding_us
+                    ):
+                        self.report(Action.IGNORE, subpath, istat, IgnoreCause.UNCHANGED)
+                        tree.items.append(source_item)
+                        continue
+
+                    sub_source_digest = source_item and source_item.digest
+                    object_type = object_type_from_mode(istat.st_mode)
+                    if object_type == b"slnk":
+                        obj = self._add_symlink(subpath, istat, source_digest=sub_source_digest)
+                        size = obj.size
+                    elif object_type == b"tree":
+                        obj = self._add_tree(subpath, istat, source_digest=sub_source_digest)
+                        size = obj.total_size
+                    elif object_type == b"blob":
+                        obj = self._add_blob(subpath, istat, source_digest=sub_source_digest)
+                        size = istat.st_size
+                    else:
+                        self.report(Action.IGNORE, subpath, istat, IgnoreCause.UNSUPPORTED_TYPE)
+                        continue
+                except Exception as err:
+                    self.report(Action.ERROR, subpath, None, err)
+                    continue
+
+                if obj:
+                    tree.items.append(TreeItem(
+                        digest = obj.digest,
+                        object_type = object_type,
+                        size = size,
+                        permissions = stat.S_IMODE(istat.st_mode),
+                        modification_timestamp_us = istat.st_mtime_ns // 1000,
+                        name = subpath.name,
+                    ))
+            elif source_item:
+                self.report(Action.REMOVE, path / source_item.name, None, source_item)
+
+        tree_object = self._repo.add_tree(tree, dry_run=self._dry_run)
+
+        action, info = Action.from_digests(tree_object.digest, source_digest)
+        self.report(action, path, pstat, info)
+        return tree_object
+
+
+    def _add_symlink(self, path: Path, pstat: stat_result, *, source_digest: Digest | None) -> SymlinkObject:
+        # TODO: Store symlink relative to current dir ?
+        #   * What about symlink that points outside of the backup dirs
+        #   * Should symlinks that points inside the backup dirs but in another
+        #     mount-point adjusted ?
+        #   * Should absolute symlink be restored as absolute ?
+        obj = self._repo.add_symlink_from_fs_target(path, path.readlink())
+
+        action, info = Action.from_digests(obj.digest, source_digest)
+        self.report(action, path, pstat, info)
+        return obj
+
+    def _add_blob(self, path: Path, pstat: stat_result, *, source_digest: Digest | None) -> BlobObject:
+        with path.open("rb") as stream:
+            obj = self._repo.add_blob(stream, dry_run=self._dry_run)
+
+        action, info = Action.from_digests(obj.digest, source_digest)
+        self.report(action, path, pstat, info)
+        return obj
+
+
+    def ignore(self, path: Path, pstat: stat_result, *, source: TreeItem | None=None) -> bool:
+        return is_bsv_repository(path)
+
+    def report(self, action: Action, path: Path, pstat: stat_result | None, info: IgnoreCause | Exception | TreeItem | None=None):
+        match action, info:
+            case (Action.ADD, None):
+                print(f"Add: {path}")
+            case (Action.UPDATE, None):
+                print(f"Add: {path}")
+            case (Action.REMOVE, item) if isinstance(item, TreeItem):
+                print(f"Remove: {path / item.name}")
+            case (Action.IGNORE, IgnoreCause.IGNORE_RULE):
+                print(f"Ignore (rule): {path}")
+            case (Action.IGNORE, IgnoreCause.UNCHANGED):
+                print(f"Ignore (unchanged): {path}")
+            case (Action.IGNORE, IgnoreCause.UNSUPPORTED_TYPE) if pstat is not None:
+                print(f"Ignore (unsupported type {path_type_name(pstat)}): {path}")
+            case (Action.ERROR, _) if isinstance(info, Exception):
+                print(f"Error {info}: {path}")
+            case _:
+                raise ValueError("TreeWalker.report(): unsupported parameter combination")
+
+
+def path_type_name(pstat: stat_result) -> str:
+    parts = []
+
+    if stat.S_ISBLK(pstat.st_mode):
+        parts.append("block_device")
+    if stat.S_ISCHR(pstat.st_mode):
+        parts.append("char_device")
+    if stat.S_ISDIR(pstat.st_mode):
+        parts.append("dir")
+    if stat.S_ISDOOR(pstat.st_mode):
+        parts.append("door")
+    if stat.S_ISFIFO(pstat.st_mode):
+        parts.append("fifo")
+    if stat.S_ISLNK(pstat.st_mode):
+        parts.append("symlink")
+    if stat.S_ISPORT(pstat.st_mode):
+        parts.append("port")
+    if stat.S_ISREG(pstat.st_mode):
+        parts.append("file")
+    if stat.S_ISSOCK(pstat.st_mode):
+        parts.append("socket")
+    if stat.S_ISWHT(pstat.st_mode):
+        parts.append("whiteout")
+
+    if not parts:
+        return "unknown"
+    return ", ".join(parts)

src/bsv/util.py

@@ -0,0 +1,118 @@
+# bsv - Backup, Synchronization, Versioning
+# Copyright (C) 2023  Simon Boyé
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from datetime import UTC, datetime as DateTime, timedelta as TimeDelta
+import os
+from pathlib import Path
+import platform
+import stat
+from typing import BinaryIO
+
+
+EPOCH = DateTime(1970, 1, 1, tzinfo=UTC)
+
+
+def time_from_timestamp_us(timestamp: int) -> DateTime:
+    return EPOCH + TimeDelta(microseconds=timestamp)
+
+def timestamp_us_from_time(time: DateTime) -> int:
+    return (time.astimezone(UTC) - EPOCH) // TimeDelta(microseconds=1)
+
+
+def read_exact(stream: BinaryIO, num_bytes: int) -> bytes:
+    data = stream.read(num_bytes)
+    if len(data) != num_bytes:
+        raise IOError(f"expected {num_bytes} bytes, got {len(data)}")
+    return data
+
+def read_exact_or_eof(stream: BinaryIO, num_bytes: int) -> bytes | None:
+    data = stream.read(num_bytes)
+    if not data:
+        return None
+    if len(data) != num_bytes:
+        raise IOError(f"expected {num_bytes} bytes, got {len(data)}")
+    return data
+
+
+def is_bsv_repository(path: Path) -> bool:
+    return (path / "bsv_repository.config").is_file()
+
+
+def object_type_from_path(path: Path) -> bytes:
+    return object_type_from_mode(path.stat(follow_symlinks=False).st_mode)
+
+def object_type_from_mode(mode: int) -> bytes:
+    if stat.S_ISLNK(mode):
+        return b"slnk"
+    elif stat.S_ISDIR(mode):
+        return b"tree"
+    elif stat.S_ISREG(mode):
+        return b"blob"
+    return b""
+
+
+def default_bsv_config_path() -> Path:
+    path = Path(os.environ.get("BSV_CONFIG", ""))
+    if path and path.is_absolute() and path.is_file():
+        return path
+    for path in user_config_dirs():
+        if path.is_file():
+            return path
+    return user_config_home() / "bsv/config"
+
+def default_local_repository_path() -> Path:
+    return user_data_home() / "bsv"
+
+
+def user_data_home() -> Path:
+    if platform.system() in ("Windows", "Darwin", "Java"):
+        raise NotImplemented(f"{platform.system()} support not implemented yet")
+    else:   # Assume Unix
+        path = Path(os.environ.get("XDG_DATA_HOME", ""))
+        if path and path.is_absolute():
+            return path
+        return Path.home() / ".local/share"
+
+def user_config_home() -> Path:
+    if platform.system() in ("Windows", "Darwin", "Java"):
+        raise NotImplemented(f"{platform.system()} support not implemented yet")
+    else:   # Assume Unix
+        path = Path(os.environ.get("XDG_CONFIG_HOME", ""))
+        if path and path.is_absolute():
+            return path
+        return Path.home() / ".config"
+
+def user_config_dirs() -> list[Path]:
+    if platform.system() in ("Windows", "Darwin", "Java"):
+        raise NotImplemented(f"{platform.system()} support not implemented yet")
+    else:   # Assume Unix
+        paths = list(filter(Path.is_absolute, map(Path, (os.environ.get("XDG_CONFIG_DIRS") or "/etc/xdg").split(":"))))
+        return [user_config_home()] + paths
+
+
+class Hash(ABC):
+    name: str
+    digest_size: int
+
+    @abstractmethod
+    def update(self, *data: bytes | bytearray | memoryview):
+        ...
+
+    @abstractmethod
+    def digest(self) -> bytes:
+        ...

tests/test_repository.py

@@ -15,16 +15,18 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 from __future__ import annotations
 from datetime import UTC, datetime
-from io import BytesIO
+from os import stat_result
 from pathlib import Path
 from random import randbytes
+from shutil import rmtree
 from typing import Iterator
 
 import pytest
 from tempfile import TemporaryDirectory
 
-from bsv.repository import Repository, Snapshot, Tree, TreeItem, create_repository, timestamp_from_time
+from bsv.repository import Repository, Snapshot, Tree, TreeItem, create_repository, timestamp_us_from_time
 from bsv.simple_cas.cas import Digest
+from bsv.tree_walker import Action, IgnoreCause, TreeWalker
 
 
 @pytest.fixture
@@ -36,8 +38,9 @@ def tmp_dir():
 @pytest.fixture
 def repo(tmp_dir):
     return create_repository(
-        tmp_dir / "bsv",
+        tmp_dir / "bsv.config",
         "test_repo",
+        tmp_dir / "bsv_repo",
     )
 
 
@@ -46,13 +49,17 @@ def test_read_write_blob(tmp_dir: Path, repo: Repository):
     make_random_file(path, 1 << 20)
 
     with path.open("rb") as stream:
-        digest = repo.add_blob(stream)
-
-    blob = repo.get_blob(digest)
-    data = blob.read()
-
+        obj0 = repo.add_blob(stream)
+    assert obj0.object_type == b"blob"
     with path.open("rb") as stream:
-        assert data == stream.read()
+        assert obj0.blob.reader().read() == stream.read()
+
+    obj1 = repo.get_blob(obj0.digest)
+    assert obj1.digest == obj0.digest
+    assert obj1.object_type == obj0.object_type
+    assert obj1.size == obj0.size
+    with path.open("rb") as stream:
+        assert obj1.blob.reader().read() == stream.read()
 
 
 def test_read_write_tree(repo: Repository):
@@ -61,40 +68,208 @@ def test_read_write_tree(repo: Repository):
         repo,
         [
             TreeItem(
-                "xyz",
-                Digest(bytes([42]) * repo._cas._digest_size),
-                0o744,
-                creation_timestamp = timestamp_from_time(now),
-                modification_timestamp = timestamp_from_time(now),
+                digest = Digest(bytes([42]) * repo._cas._digest_size),
+                object_type = b"blob",
+                size = 123,
+                permissions = 0o744,
+                modification_timestamp_us = timestamp_us_from_time(now),
+                name = "xyz",
             ),
             TreeItem(
-                "foobar",
-                Digest(bytes([123]) * repo._cas._digest_size),
-                0o777,
-                creation_timestamp = timestamp_from_time(now),
-                modification_timestamp = timestamp_from_time(now),
+                digest = Digest(bytes([123]) * repo._cas._digest_size),
+                object_type = b"slnk",
+                size = 42,
+                permissions = 0o777,
+                modification_timestamp_us = timestamp_us_from_time(now),
+                name = "foobar",
             ),
         ]
     )
 
     assert Tree.from_bytes(repo, tree.to_bytes()) == tree
 
-    digest = repo.add_tree(tree)
-    assert repo.get_tree(digest) == tree
+    obj0 = repo.add_tree(tree)
+    assert obj0.object_type == b"tree"
+    assert obj0.tree == tree
+
+    obj1 = repo.get_tree(obj0.digest)
+    assert obj1.digest == obj0.digest
+    assert obj1.object_type == obj0.object_type
+    assert obj1.size == obj0.size
+    assert obj1.tree == obj0.tree
 
 
 def test_read_write_snapshot(repo: Repository):
     snapshot = Snapshot(
         repo = repo,
         tree_digest = Digest(bytes([42]) * repo._cas._digest_size),
+        parents = [
+            Digest(bytes([123]) * repo._cas._digest_size),
+            Digest(bytes([124]) * repo._cas._digest_size),
+        ],
         repo_name = "test_repo",
-        timestamp = timestamp_from_time(datetime.now()),
+        timestamp_us = timestamp_us_from_time(datetime.now()),
     )
 
     assert Snapshot.from_bytes(repo, snapshot.to_bytes()) == snapshot
 
-    digest = repo.add_snapshot(snapshot)
-    assert repo.get_snapshot(digest) == snapshot
+    obj0 = repo.add_snapshot(snapshot)
+    assert obj0.object_type == b"snap"
+    assert obj0.snapshot == snapshot
+
+    obj1 = repo.get_snapshot(obj0.digest)
+    assert obj1.digest == obj0.digest
+    assert obj1.object_type == obj0.object_type
+    assert obj1.size == obj0.size
+    assert obj1.snapshot == obj0.snapshot
+
+
+class TestTreeWalker(TreeWalker):
+    reports: list
+
+    def __init__(self, repo: Repository, dry_run: bool=False):
+        super().__init__(repo, dry_run=dry_run)
+        self.reports = []
+
+    def report(
+        self,
+        action: Action,
+        path: Path,
+        pstat: stat_result | None,
+        info: IgnoreCause | Exception | None = None
+    ):
+        super().report(action, path, pstat, info)
+        self.reports.append((action, path, info if action != Action.REMOVE else None))
+
+
+def test_add_tree(tmp_dir: Path, repo: Repository):
+    dir = tmp_dir / "test0"
+    structure0 = {
+        "folder": {
+            "sub_folder": {
+                "empty_folder": {},
+                "foo.txt": b"Hello World!\n",
+            },
+            "test.py": b"print(\"Hello World!\")\n",
+            "bar.dat": bytes(range(256)),
+        },
+        "Another test with long name and spaces and a bang !": b"Should works.\n",
+        "bsv_repo": {
+            "bsv_repository.config": b"[bsv]\n",
+        },
+    }
+    structure1 = {
+        "folder": {
+            "sub_folder": {
+                "empty_folder": {},
+                "foo.txt": b"Hello World!\n",
+            },
+            "bar.dat": bytes(range(256)) * 2,
+        },
+        "new_file": b"whatever",
+        "Another test with long name and spaces and a bang !": b"Should works.\n",
+        "bsv_repo": {
+            "bsv_repository.config": b"[bsv]\n",
+        },
+    }
+
+    expected0 = dict(structure0)
+    del expected0["bsv_repo"]
+
+    expected1 = dict(structure1)
+    del expected1["bsv_repo"]
+
+    create_file_structure(dir, structure0)
+
+    def check(digest: Digest, value: dict | bytes):
+        if isinstance(value, dict):
+            tree = repo.get_tree(digest).tree
+            assert tree
+            assert list(map(lambda i: i.name, tree.items)) == sorted(value.keys())
+            for item in tree.items:
+                check(item.digest, value[item.name])
+        elif isinstance(value, bytes):
+            blob_obj = repo.get_blob(digest)
+            data = blob_obj.blob.reader().read()
+            assert data == value
+
+    walker = TestTreeWalker(repo)
+    obj0 = walker.add_tree(dir)
+    assert obj0.object_type == b"tree"
+    assert walker.reports == [
+        (Action.ADD, dir / "Another test with long name and spaces and a bang !", None),
+        (Action.IGNORE, dir / "bsv_repo", IgnoreCause.IGNORE_RULE),
+        (Action.ADD, dir / "folder/bar.dat", None),
+        (Action.ADD, dir / "folder/sub_folder/empty_folder", None),
+        (Action.ADD, dir / "folder/sub_folder/foo.txt", None),
+        (Action.ADD, dir / "folder/sub_folder", None),
+        (Action.ADD, dir / "folder/test.py", None),
+        (Action.ADD, dir / "folder", None),
+        (Action.ADD, dir, None),
+    ]
+    check(obj0.digest, expected0)
+
+    create_file_structure(dir, structure1)
+
+    walker.reports.clear()
+    obj1 = walker.add_tree(dir, source_digest=obj0.digest)
+    assert obj0.object_type == b"tree"
+    assert walker.reports == [
+        (Action.IGNORE, dir / "Another test with long name and spaces and a bang !", IgnoreCause.UNCHANGED),
+        (Action.IGNORE, dir / "bsv_repo", IgnoreCause.IGNORE_RULE),
+        (Action.UPDATE, dir / "folder/bar.dat", None),
+        (Action.IGNORE, dir / "folder/sub_folder/empty_folder", IgnoreCause.UNCHANGED),
+        (Action.IGNORE, dir / "folder/sub_folder/foo.txt", IgnoreCause.UNCHANGED),
+        (Action.IGNORE, dir / "folder/sub_folder", IgnoreCause.UNCHANGED),
+        (Action.REMOVE, dir / "folder/test.py", None),
+        (Action.UPDATE, dir / "folder", None),
+        (Action.ADD, dir / "new_file", None),
+        (Action.UPDATE, dir, None),
+    ]
+    check(obj1.digest, expected1)
+
+
+def create_file_structure(dst: Path, value: dict | bytes):
+    if isinstance(value, bytes):
+        if dst.is_dir():
+            rmtree(str(dst))
+        if not dst.is_file() or dst.read_bytes() != value:
+            dst.write_bytes(value)
+    elif isinstance(value, dict):
+        if dst.is_file():
+            dst.unlink()
+        if not dst.is_dir():
+            dst.mkdir()
+
+        items = sorted(value.items())
+        fs_paths = sorted(dst.iterdir())
+
+        item_index = 0
+        fs_path_index = 0
+
+        while item_index < len(value) or fs_path_index < len(fs_paths):
+            name, subitem = items[item_index] if item_index < len(items) else (None, None)
+            fs_path = fs_paths[fs_path_index] if fs_path_index < len(fs_paths) else None
+
+            if name and fs_path:
+                if name < fs_path.name:
+                    fs_path = None
+                elif name > fs_path.name:
+                    name = None
+
+            if name:
+                item_index += 1
+            if fs_path:
+                fs_path_index += 1
+
+            if name:
+                create_file_structure(dst / name, subitem) # type: ignore
+            elif fs_path and fs_path.is_dir():
+                rmtree(fs_path)
+            elif fs_path:
+                fs_path.unlink()
+    else:
+        raise TypeError(f"invalid type {type(value).__name__} for parameter value")
 
 
 def make_random_file(path: Path, size: int):

tests/test_simple_cas.py

@@ -55,7 +55,9 @@ def test_simple_cas(tmp_dir: Path):
 
         obj = cas.read(digest)
         assert obj is not None
+        assert obj.digest == digest
         assert obj.object_type == b"blob"
+        assert obj.size == len(data)
         assert obj.data == data
 
     cas = SimpleCas(
@@ -68,7 +70,9 @@ def test_simple_cas(tmp_dir: Path):
 
         obj = cas.read(digest)
         assert obj is not None
+        assert obj.digest == digest
         assert obj.object_type == b"blob"
+        assert obj.size == len(data)
         assert obj.data == data
 
         digest2 = cas.write(b"blob", data)